1. Field of the Invention
This invention relates generally to computer and communication networks. More specifically, it relates to a portable reach-back communications system that provides extremely flexible secure or non-secure voice, video and data services to a remote user.
2. Background of the Related Art
In 1970, the Secure Telephone Unit (STU-I) was developed, followed in 1975 by the STU-II, and finally in 1987 by the third generation STU-III.
The STU-III terminals are designed to operate as either an ordinary telephone or a secure instrument over a dial-up public switched telephone network (PSTN). The STU-III operates in full-duplex over a single telephone circuit using echo canceling modem technology. Typically, STU-IIIs come equipped with 2.4 and 4.8 kbps code-excited linear prediction (CELP) secure voice. Secure data can be transmitted at speeds of 2.4, 4.8 and 9.6 kbps, though data throughput between two STU-IIIs is only as great as the slowest STU-III.
A STU-III operates by taking an audio signal and digitizing it into a serial data stream, which is then mixed with a keying stream of data created by an internal ciphering algorithm. This mixed data is then passed through a COder-DECoder (CODEC) to convert it back to audio so it can be passed over the phone line. STU-IIIs also allow a serial data stream to pass through the phone and into the ciphering engine to allow its usage as an encrypted modem when not used for voice.
The keying stream is a polymorphic regenerating mathematic algorithm which takes an initialization key and mathematically morphs it into a bit stream pattern. The keying stream is created by the key generator, and is the heart of the STU-III. A portion of the keying stream is then mixed back into the original key, and the process is repeated. The result is a pseudo-random bit stream that if properly implemented is extremely difficult to decrypt. Even the most sophisticated cryptographic algorithm can be easily expressed in the form of a simple equation in Boolean algebra, with the initialization keys being used to define the initial key generator settings, and to provide morphing back to the equation.
While STU-III provides secure communications, audio quality was vastly improved with the development of purely digital Standard Telephone Equipment (STE) devices.
An STE device utilizes an ISDN digital telephone line connection. There is substantial improvement in voice quality using an STE as opposed to the STU-III used over analog telephone lines. Most STE devices are STU-III secure mode compatible with enhanced abilities including voice-recognition quality secure voice communication, and high-speed secure data transfers (up to 38.4 kbps for asynchronous or 128 kbps for synchronous data transfers). When connected to an analog telephone line, an STE unit will only support STU-III voice and data capabilities.
The STU-III and STE are quite useful in fixed use, i.e., in an office environment or perhaps carried to another location having access to analog or digital telephone line access.
FIG. 18 is a depiction of a conventional fragmented secure communications network.
In particular, as shown in FIG. 18, a network backbone 1800 allows various like devices to securely connect to each other. The network backbone 1800 includes such communication networks as ISDN TDM, ATM and IP. Devices that can connect to the network backbone 1800 include an ISDN telephone 1810, a voice-over-IP computer terminal 1820, a voice-over-IP telephone 1830, TRI-TAC & MSE devices 1840, cellular telephones 1850, communicating use using various standards including CDMA, GSM, TDMA and iDEN. Other devices that can connect to the network backbone 1800 include tactical digital radios 1850, analog cellular telephones 1860, satellite communications 1870, a dial-up computer terminal 1880, and a public switched telephone network telephone 1890.
In operation, each of the devices transmitting data to the network backbone 1800 must encrypt their respective data streams. Each of the devices receiving data from the network backbone 1800 must un-encrypt their respective data streams.
A conventional vocoder for use with the network backbone 1800 is the Mixed-Excitation Linear Predictive (MELP) vocoder. THe MELP vocoder is a dual-rate low rate coder that operates at 1200 bits-per-second (bps) and 2400 bps. The MELP vocoder meets military standard MIL-STD-3005 and NATO STANAG 4591.
FNBDT is an acronym that corresponds to Digital Secure Voice Protocol (DSVP) transport layer and above. DSVP operates over most data and voice network configurations with a Least Common Denominator for interoperability. DSVP interoperates with many media including wireless, satellite, IP and cellular. DSVP adapts to the data rate of the connection, with modems training down. DSVP negotiates security/application features with application to point-to-point communications and multi-point communications. DSVP supports realtime, near realtime and non-realtime applications.
FIG. 19 is a depiction of a conventional combination wired and wireless communication network supporting secure communications. Secure operation requires wireless circuit switched data service and use of a data telephone number.
In particular, as shown in FIG. 19, a combination wired and wireless communication network comprises various analog and digital communication networks 1900, such as PSTN 1901, analog communication networks 1902 and digital communication networks 1903. Devices connecting to the various analog and digital communication networks 1900 include mobile satellite service devices 1910 connecting to a satellite service 1911, e.g., Iridium, Globalstar and ICO. The mobile satellite service devices 1910 communicate through a Iridium satellite system. Further devices connecting to the various analog and digital communication networks 1900 include an STE 1920, digital cellular telephones 1930 using, e.g., GSM standards, digital cellular telephones 1940 connecting to a CDMA network. A tactical MSE/TRI-TAC network 1950 allows various devices to connect to the various communication networks 1900. Devices connecting to the tactical MSE/TRI-TAC network 1950 are, e.g., JTR 1952, deployable LMR 1954 and cellular tactical STE 1956. The tactical MSE/TRI-TAC network 1950 can connect to a CDMA network. A STU-III 1970 and analog cellular telephone 1972, e.g., CipherTAC 2000, connect to the analog network 1902.
In operation, CDMA communications occur at 800 Mhz over CONUS approved networks, such as Verizon and ALLTEL. GSM communications occur at 900 Mhz, 1800 Mhz and 1900 Mhz over CONUS approved networks, such as T-Mobile and AT&T. OCONUS European GSM, many approved based on commercial approval of TimeportII GSM phone within SECTRA-GSM secure terminal.
Any of the communication devices of FIG. 19 can obtain a secure voice connection with any secure, like communication device.
FIG. 20 is a depiction of a conventional deployable secure communication system utilizing a satellite communication network.
In particular, as shown in FIG. 20, a secure encryption STE 700 with suitable interface hardware is utilized to provide a connection path to a wireless connection to a similarly secure STE via a satellite transceiver 914, e.g., an Inmarsat M4 terminal. In the conventional system of FIG. 20, an ISDN link is utilized between the STE 700 and a suitable satellite two-way communication transceiver and antenna 914.
In operation, voice data is encrypted by the STE 700, and transmitted in a secure environment over a physically secure satellite, e.g., the M4 INMARSAT satellite transceiver 914.
It is vitally important that the STE 700 stay physically secured, to maximize protection of the information being passed thereover. Also, to further maximize protection of the information, the satellite transceiver 914 is conventionally set up and maintained within a secure environment, and usually travels with the STE 700.
Conventional systems are typically physically large, e.g., the size of a van. More importantly, such conventional systems require all elements to be maintained in a secure environment, including the data transport system (e.g., satellite communication system) over which the data travels to another secure communications terminal. Such secure data transport systems are costly to install and maintain, and always run a risk of being compromised.
FIG. 21 is a depiction of a conventional CDMA to GSM secure call setup.
In particular, before two-party secure voice traffic starts, FNBDT Call Setup Application messages are exchanged using an FNBDT Application Reliable Transport and Message Layer Protocols.
FIG. 22 is a depiction of a conventional FNBDT example call.
In particular, FNBDT secure voice & data may be sent over may network segments. The connection shown use CDMA, PSTN and GSM networks.
The prior art uses a plurality of different devices, one for connection to each network that a user desires to connect with. Thus, there is a need for a small, lightweight, easily portable and easily deployable communication system that is not only even more secure than conventional systems, but which also allows flexibility in use of non-secure data transport systems.
Such conventional secure systems are typically physically large but more importantly allow for only direct secure connection communication between a remote user and a like receiver to maintain security in the communications. While this is quite useful in many situations, only limited communications are possible in a direct connection. For instance, direct, secure connectivity does not also allow access to non-secure public communication systems, e.g., the Internet.
There is a need for a small, lightweight, and extremely flexible and adaptable communications terminal capable of quick, convenient and easy use with a multitude of network environments, and for a deployable communication system that is not only more secure than conventional systems, but which also allows flexibility in use of non-secure data transport systems.